Switched-fabric communication architectures are widely used in high-performance computing. Examples of such architectures include InfiniBand™ and high-speed Ethernet™. Aspects of these architectures will be described here by way of illustration (and implementation of an embodiment of the present invention in the Ethernet environment will be described below in the Detailed Description), but it should in no way be understood that the present invention is limited to one particular type of switched fabric or another.
Computing devices (host processors and peripherals) connect to the switched fabric via a network interface controller (NIC), which is referred to in InfiniBand (IB) parlance as a channel adapter. Host processors (or hosts) use a host channel adapter (HCA), while peripheral devices use a target channel adapter (TCA). Client processes (referred to hereinafter as clients), such as software application processes, running on a host processor communicate with the transport layer of the fabric by manipulating a transport service instance, known as a “queue pair” (QP), which is made up of a send work queue and a receive work queue. To send and receive messages over the network using a HCA, the client submits work items, called work queue elements (WQEs), for execution by the HCA. (More precisely, the client initiates work requests (WRs), which cause WQEs to be placed in the appropriate work queues.) After it has finished servicing a WQE, the HCA typically writes a completion report, in the form of a completion queue element (CQE), to a completion queue, to be read by the client as an indication that the work request has been executed.
Although the above terminology and some of the embodiments in the description that follows are based on features of the IB architecture and use vocabulary taken from IB specifications, similar mechanisms exist in networks and I/O devices that operate in accordance with other protocols, such as Ethernet and Fibre Channel. The IB terminology and features are used herein by way of example, for the sake of convenience and clarity, and not by way of limitation.